1. Field of the Invention
The present invention relates generally to in-flight entertainment (IFE) systems, and more particularly to IFE systems that provide on a world-wide basis live video/audio programming to passengers/operators of an aircraft using broadcast signals transmitted in either circular or linear polarized form.
2. Description of the Related Art
Conventional IFE systems, that distribute live video/audio programming to aircraft passengers, such as an Airborne Satellite Television System (ASTS) manufactured by the assignee of the present invention, derive the live video/audio programming signals from a direct broadcast satellite (DBS) that transmits broadcast signals in the form of right and left circular polarized RF signals. For example, U.S. Pat. No. 5,790,175, issued on Aug. 4, 1998, entitled xe2x80x9cAircraft Satellite Television System for Distributing Television Programming Derived From Direct Broadcast Satellites,xe2x80x9d and U.S. Pat. No. 5,801,751, issued on Sep. 1, 1998, entitled xe2x80x9cDistribution of Satellite Television Programs to Passengers in an Aircraft When It Is Out of Range of the Satellites,xe2x80x9d the disclosures of which are incorporated by reference herein, describe an IFE system that provides live television programming derived from signals broadcast by the DIRECTV DBS system.
Conventional IFE systems, however, are limited because they cannot derive live video/audio programming signals if DBS signals are not in the form of right and left circular polarized RF signals. Although DBS systems that provide service within the continental United States broadcast signals in the form of right and left circular polarized RF signals, DBS systems whose service regions lie outside North and South America generally broadcast signals in the form of horizontal and vertical linear polarized RF signals. For this reason, conventional IFE systems are unable to provide live video/audio programming when the aircraft travels outside the continental United States and into regions serviced by these DBS systems.
In co-pending U.S. Patent Application entitled xe2x80x9cPassenger Entertainment System Providing Live Video/Audio Programming Derived from Satellite Broadcasts,xe2x80x9d the contents of which are incorporated by reference herein, an IFE system that is capable of deriving video/audio programming signals from satellite broadcast signals transmitted in either the circular polarized form or the linear polarized form is disclosed. This system is able to derive the video/audio programming signals from satellite broadcast signals transmitted by satellite constellations within any geographical region, so that live video/audio programming may be distributed to aircraft passengers on a worldwide basis.
An object of the present invention is to provide an IFE system that derives video/audio programming signals from satellite broadcast signals transmitted either in circular polarized form or linear polarized form, using an intermediate frequency (IF) signal generating unit that receives downconverter control signals and DC power over IF signal output cables.
Another object of the present invention is to provide a method of producing IF signals from satellite broadcast signals using downconverter control signals and DC power that are delivered over IF signal output cables.
The above and other objects are achieved by diplexing the downconverter control signals and DC power onto the IF signal output cables. By using the IF signal output cables as input lines for the downconverter control signals and DC power, the wiring structure is greatly simplified in the IFE system according to the present invention. This results in valuable weight savings for the aircraft. Additionally, the IFE system according to the present invention employs: a pair of bias-T connectors that are arranged in the IF signal output cables. The bias-T connectors permit the IF signals that are generated by the downconverter to be supplied over the output cables in a first direction while extracting the downconverter control signals and DC power that are received in a second direction which is opposite to the first direction.
Additional objects, features and advantages of the invention will be set forth in the description of preferred embodiments which follows.